DE102009040523A1 - Thermal engine for driving e.g. generator, has energy storage arranged at rotor, where energy storage is chargeable in heat source by changing shape of shape memory element and dischargeable at peripheral position outside of heat source - Google Patents

Abstract

The thermal engine (1) has a rotor (2) rotatable around an axis of rotation (3), and an energy storage (13) arranged at the rotor, where the energy storage is attached to a shape memory element (9) i.e. wire, of the rotor. The shape memory element is movable between a heat source (4) and a heat sink (5) by rotating the rotor. The energy storage is chargeable in the heat source by changing shape of the shape memory element and dischargeable at a defined peripheral position (18) outside of the heat source. Blocking units (15) are attached at the energy storage.

Description

The invention relates to a heat engine with a rotatable about a rotation axis rotor, comprising at least one shape memory element which is adjustable by rotating the rotor between at least one heat source and at least one heat sink.

In the case of shape memory alloys, the prerequisite for the occurrence of the so-called shape memory effect is that a reversible and diffusionless austenitic-martensitic phase transformation takes place. In this case, the high-temperature phase is usually referred to as austenite and the low-temperature phase as martensite. The diffusionless martensitic transformation essentially represents a shearing of the austenitic lattice that occurs during cooling. One form of the shape memory effect is the so-called one-way effect, in which a previously thermomechanically embossed shape is restored by heating the shape memory alloy. If a component made of a shape memory alloy in the martensitic state is permanently deformed in the region below a critical degree of deformation, martensite deformation takes place by shifting highly mobile twin boundaries. This process is reversible. Since the one-way effect of a cooling of the component no further deformation brings with it, one speaks of the one-way effect - to repeat the effect, the martensite must be deformed again under force. In addition to the one-way effect, there is the so-called two-way effect. Two-way effect components can not only "remember" a high temperature shape, but also a particular shape in the low temperature phase. In contrast to the one-way effect, there is a macroscopic change in shape even during the non-mechanically loaded state during the lattice transformation. The material is reminiscent of both its shape in the austenitic and in the martensitic structure.

The one-way effect is based on the principle of operation of a so-called swashplate heat engine. This has appeared in the edition published in the Expertverlag "shape memory alloys", Volume 655 series "Contact & study". The swashplate heat engine developed at the FH Konstanz represents an engine principle which can transform low-temperature heat into mechanical energy by means of shape-memory metals. The machine consists of a plurality of shape memory wires (shape memory elements) which are mounted distributed between two mutually inclined discs over the circumference. The discs in turn are fixed on two separate shafts, which are connected to each other via a universal joint. The machine is divided into a heat source and a heat sink. The shape memory elements are the drive in which they are alternately heated and cooled. They are claimed only on train. Within the heat sink, in which the wires are in the martensitic state and thus are "soft", they are expanded by tilting the disc under low tension. The angle of the inclined disc is adjusted so that the wires are elongated by up to 5%. Within the heat source, the shape memory wires contract again, exerting a force on the two discs. The result is a force acting in the tangential direction, which ensures the rotation of the machine.

The known heat engine has been proven - but their efficiency is relatively low, since only about 3% of the deformation energy of the shape memory elements are converted into rotational energy. In addition, the structure is relatively complex and there are due to the high-acting axial forces highest demands on the necessary universal joint, which angles the two discs to each other.

In addition to the prior art described above are in the DE 198 10 639 A1 , of the DE 198 10 640 C2 and the EP 0 919 717 A1 Linear drives using the shape memory effect known.

Based on the aforementioned prior art, the present invention seeks to provide a rotationally operating heat engine with high efficiency. Preferably, the heat engine should be characterized by a simplified structure. Moreover, the object is to provide a system comprising a correspondingly optimized heat engine and a device driven by the heat engine.

This object is achieved in a generic heat engine, characterized in that the shape memory element is associated with at least one arranged on the rotor energy storage, which is chargeable in the heat source by the change in shape of the shape memory element and at a defined circumferential position outside the heat source is discharged.

With regard to the system, the invention is achieved by the use of a trained according to the concept of the invention heat engine.

Advantageous developments of the invention are specified in the subclaims. In the context of the invention, all combinations of at least two of in the description, the Claims and / or the figures disclosed features. In order to avoid repetition, features disclosed according to the device should be regarded as disclosed according to the method and be able to be claimed. Likewise, according to the method disclosed features should be considered as device disclosed and claimed claimable.

The invention is based on the idea of assigning to the at least one rotatably arranged shape memory element a, preferably mechanical, energy store which allows the energy released during the change in shape, preferably during contraction, of the shape memory element to be stored in the heat sink so that it continues in the circumferential direction can be transported, namely out of the heat sink, which has caused the change in shape of the shape memory element out to be discharged at least one defined circumferential position. In this case, the invention is based on the finding that the efficiency of a heat engine based on the shape memory effect can be substantially increased by not utilizing or utilizing a force component acting in the tangential direction as in the prior art, but rather a force component acting in the direction of deformation of the shape memory element , By temporarily storing the energy released during the change in shape, preferably when contracting, the shape memory element is suddenly transportable and can be discharged at a defined peripheral position, preferably in a pulse-like manner, in particular in a linear movement. In other words, the energy storage can remain in the charged state, although the associated therewith, at least one shape memory element has already been relaxed or lengthened again in the heat sink. An embodiment variant of the heat engine in which the latter does not have a single shape memory element but a plurality of shape memory elements, in particular uniformly distributed over the circumference of the rotor, is even more preferred. More preferably, the shape memory elements, preferably all shape memory elements, are an energy store. Latch) is assigned, wherein the energy storage, the temporarily stored energy, in particular in the form of kinetic energy, offset in time at the defined circumferential position, in particular pulse-like outputs. It is also conceivable that the cached energy at at least two different circumferential positions, in particular pulse-like, is released. It is even more preferable for the energy released at the at least one defined circumferential position, preferably in a linear movement, to be converted into another form of energy and / or movement, in particular into a rotational movement and / or into electrical energy. For this purpose, the at least one defined circumferential position are preferably assigned corresponding means, for example a crank drive and / or a generator, etc.

It is particularly preferred if the circumferential position at which the energy storage discharges, immediately - viewed in the circumferential direction - is arranged in front of the heat source, so that the energy storage is recharged after discharging by immersing the at least one shape memory element associated with it in the heat source ,

The heat engine proposed here is not limited to a variant in which it is provided with only a single heat source and with a single heat sink. In particular, depending on the diameter of the rotor, the rotor can be associated with a plurality of heat sources and heat sinks, wherein it is preferred if heat sinks and heat sources are arranged alternately in the circumferential direction.

A further significant advantage of a heat engine designed according to the concept of the invention is that it can be constructed much simpler, since the provision of two shafts arranged at an angle to one another and thus to a joint arranged between the shafts, for example a universal joint, can be dispensed with.

In a further development of the invention is advantageously provided that the energy storage of the at least one shape memory element is associated with blocking means which are designed to prevent energy discharge of the energy storage before reaching the defined circumferential position. If the energy store is designed, for example, as a spring, in particular as a helical spring, then the blocking means hold the spring in the tensioned, preferably compressed, state until the defined circumferential position at which the energy store is to be discharged is reached. Most preferably, the blocking means are designed such that they allow a discharging of the energy storage just before immersing the shape memory element associated therewith in the heat source. This may be provided, for example, by the provision of a support track which extends in the circumferential direction and on which the energy stores are supported axially to prevent discharge. In this case, this support web should preferably end shortly before reaching the heat source or change its shape such that the energy storage is discharged.

Very particular preference is given to a variant of the heat engine in which the, in particular mechanical, energy storage Spring element comprises or consists of a spring element. In this case, both an embodiment can be realized in which the spring is compressed by contraction of the shape memory element, as well as an embodiment in which the spring is deflected by contraction of the shape memory element. It is only essential that a tensioning, ie a charging of the energy storage by contraction of the at least one shape memory element within the heat source results.

Very particularly preferred is a variant in which the clamping movement of the spring element, at least approximately, linear, very particularly preferably, at least approximately, preferably exactly, parallel to the axis of rotation of the rotor.

It is particularly expedient with regard to the realization of the simplest possible structure and the achievement of optimum efficiency, if the at least one energy storage element associated with the shape memory element as an elongated element, in particular as a wire, or at least one wire comprises or consists of several Composed wires and extends parallel to the axis of rotation of the rotor, at least in the tensioned state, d. H. inside the heat source. It is particularly useful if the shape memory element is associated with a, preferably substantially, lower spring constant than the spring constant of the spring of the energy store having tension spring, which ensures that the shape memory element in the relaxed state, d. H. within the heat sink, at least somewhat tensioned mechanically to avoid an uncontrolled "fluttering" during the preferably fast rotational movement of the rotor.

It is particularly useful if the shape memory element between two parallel, extending transversely to the axis of rotation of the rotor, for example, disc and / or annular holding elements is arranged, wherein the holding elements are spaced apart in the direction of the longitudinal extent of the axis of rotation of the rotor. On the inclination of one of the holding elements as in the known swash plate heat engine can be dispensed with advantage.

As already indicated above, it is particularly preferred if means for converting the energy emitted by the shape memory element at the defined circumferential position into another energy form, for example electrical energy, are provided and / or if means for converting the, preferably linear, relaxation movement of a spring element comprehensive energy storage are provided in a rotational movement. For this purpose, for example, a crank mechanism is suitable.

In order for the rotor to be able to transport the shape memory element from the heat sink to the heat source in the circumferential direction, the rotor has to be driven in the circumferential direction. This can be done, for example, with a completely self-sufficient by the heat engine, separate drive motor, such as an electric motor or an internal combustion engine, the drive is powered by some kind of separate energy source. It is also conceivable to realize a, in particular mechanical or electrical, feedback, in such a way that the rotor or the drive of the rotor is supplied with energy which originates from the relaxation of the shape memory element or from the energy store. Thus, for example, it is conceivable that by means of the heat engine, a generator is driven, which generates electrical energy, which supplies either directly, or stored for example via a battery an electric motor drive for the rotor. Alternatively, a mechanical feedback, for example via a crank mechanism and / or a transmission can be realized.

With regard to the configuration of the shape memory element, there are different possibilities. It is very particularly preferred to form the shape memory element made of metal, that is to say a metallic shape memory alloy. Additionally or alternatively, so-called shape memory polymers can be used.

As already indicated, it is particularly preferred if the rotor has a multiplicity of shape-memory elements, which are preferably uniformly spaced in the circumferential direction. In this case, both an embodiment can be realized in which all, the shape memory elements associated energy storage deliver their energy at the same defined circumferential position of the rotor, or at different, preferably circumferentially spaced, positions. The latter can for example be realized in that shape memory elements are arranged on two concentric circular rings and the trigger positions are spaced in the radial direction and / or in the circumferential direction. It is very particularly preferred if the discharge of the energy store takes place at different positions at the same time and, for example, together a camshaft is driven with differently oriented cams.

It is particularly useful if the maximum temperature in the heat source during operation of the heat engine is less than 100 ° C and preferably higher than 80 ° C and / or that the temperature of the heat sink is less than 60 ° C, so that waste heat from stationary processes, such as waste heat from power plants or internal combustion engines for driving the heat engine or for heating the heat source can be used. It is very particularly preferred if the heat source is realized by a water bath and / or the heat sink is from an air bath, preferably at ambient temperature. To accelerate the evaporation of the water in the heat sink, for example, an artificial air flow, in particular by means of at least one fan wheel, are generated.

The invention also leads to a system comprising at least one heat engine designed as described above. In this case, several heat engines can be provided. The at least one heat engine drives at least one device, for example a generator, a pump or a vehicle, etc.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawings.

These show in:

1 and

2 Two different perspective views of an embodiment of a heat engine, in which a plurality of shape memory elements each energy (between) memory is assigned. By way of example only, the heat engine in the illustration comprises 1 a crank mechanism for converting a generated during the energy discharge of the energy storage linear motion in a rotational movement, for example, for driving a rotary generator (not shown).

In the figures, like elements and elements having the same function are denoted by the same reference numerals.

The 1 and 2 show a heat engine 1 with a rotor 2 that is about a rotation axis 3 is rotatably arranged. Furthermore, the heat engine includes 1 a, here formed by a water bath heat source 4 and a heat sink formed by ambient air and utilizing evaporative cooling 5 , In the embodiment shown, heat source extend 4 and heat sink 5 each over about 180 ° of the circumferential extent of the rotor 2 ,

The rotor 2 comprises two disc-like holding elements 6 . 7 extending in the direction of the longitudinal extent of a concentric to the axis of rotation 3 extending wave 8th of the rotor 2 spaced apart. The holding elements 6 while sitting on the shaft rotatably 8th ,

Between the holding elements 6 . 7 extend a plurality, each having a plurality of shape memory alloy wires comprehensive shape memory elements 9 , These are arranged uniformly spaced in the circumferential direction and sit on an imaginary cylinder jacket, wherein the shape memory elements 9 parallel to the axis of rotation 3 and with it to the wave 8th extend.

With their respective left in the plane of the drawing end are the shape memory elements 9 each with a pole 10 connected, which has a through hole 11 of the holding element 7 penetrated and passed further in the axial direction by a spring designed as a helical spring 12 that is part of an energy store 13 , Which are parallel to the axis of rotation 3 and with it to the wave 8th extending feathers 12 are based with their respective the holding element 7 facing axial end on the holding element 7 from and with their respective from the holding element 7 opposite end to a, here cylindrical, abutment 14 , which firmly with the rod 10 connected is.

Will now be the rotor 2 around the axis of rotation 3 Rotationally driven, so are the shape memory elements 9 transported in the circumferential direction and get away from the heat sink 5 to the heat source 4 and back to the heat sink 5 , Etc.

By immersion in hot water, for example, about 90 ° C, ie by immersion in the heat source 4 , becomes the shape memory elements 9 added thermal energy, which causes a lattice transformation of martensite in austenite, so that the shape memory elements 9 inside the heat source 4 contract, ie contract. As a result, the rods become 10 moved in the drawing plane to the right and thus also the abutment 14 so the springs 12 linearly stretched, so the energy storage 13 to be charged. Now become the contracted shape memory elements 9 moved further in the circumferential direction and get into the sequence in the heat sink 5 into, cool and relax, ie, lengthen due to a lattice transformation of austenite into martensite. To prevent the shape memory elements 9 associated springs 12 In this way also directly relax, ie can length, or to prevent the energy storage 13 are discharged immediately, are the energy storage 13 blocking agent 15 assigned. These include a non-circumferentially closed, non-rotatable with the shaft 8th connected part ring formed ring track 16 , on the firm with the abutments 14 associated roles 17 can roll in the circumferential direction. The position of the blocking agent 15 , ie the circular path 16 is sized so that the springs 12 as long as she is at the ring track 16 support, can not relax.

Just before the shape memory elements 9 back to the heat source 4 can dive, is the ring track 16 interrupted, ie the blocking means end 15 , This (circumferential) position is denoted by the reference numeral 18 characterized. Reached a shape memory element 9 , more precisely, the associated energy storage 13 the circumferential position 18 , this can discharge impulsively, as the spring 12 suddenly linearly parallel to the longitudinal extent of the axis of rotation 3 can relax. This presses the spring 12 on an attack surface 19 a linearly movable part 20 , here a pole 10 , which is mounted linearly displaceable. Because the rotor 2 rotatably driven meet in succession all circumferentially spaced energy storage 13 at the position 18 one and discharge there (one after the other) abruptly and displace the part in each case 20 in the axial direction parallel to the axis of rotation 3 , This linear movement of the part 20 can be exploited in many ways. For example, the linear motion, as in 1 is indicated schematically, via a crank mechanism 21 that with the part 20 is operatively connected, in a rotational movement about an axis 22 being transformed. This rotational movement 22 In turn, for example, a device, in particular a generator, drive. It is also conceivable, directly the linear movement of the part 20 to use for driving a device, such as a linear generator. In the only schematically illustrated, the simplest embodiment of a crank mechanism 21 is a crank 23 both articulated with the part 20 as well as articulated with a rotatably mounted wheel 24 connected.

After discharge, the shape memory elements become 9 with associated energy storage 13 continue in the circumferential direction back into the heat source 4 transported, wherein in the initial area, that is immediately after immersion not the blocking agent 15 are located. Inside the heat source 4 become the shape memory elements 9 contracted again and the associated spring 12 curious, ie the associated energy storage 13 charged, causing the associated abutment 14 and thus the associated role 17 in the drawing plane to the right, ie in the direction of holding elements 6 . 7 moved and still within the heat source 4 is transported to a circumferential position (not shown), starting from the associated role 17 again at the blocking agents 15 , here at the Ringbahn 16 can support a premature discharge of energy storage 13 in the heat sink 5 to prevent.

Merely for the sake of completeness it should be mentioned that the shape memory elements 9 with that of the energy stores 13 opposite ends on each rod 25 are fixed, with the bars 25 one hole each 26 in the right in the plane of the drawing holding element 6 push through. The bars 25 have a widened in the radial direction free end 27 on, leaving axially between the end 27 and the holding element 6 a tension spring, not shown, can be provided, which has a much lower spring constant than the spring 12 an energy store 13 , The tension spring, not shown, serves the respective shape memory element 9 to tension something, so that this the rotational movement of the rotor 2 can not interfere.

LIST OF REFERENCE NUMBERS

1

Heat engine

2

rotor

3

axis of rotation

4

heat source

5

heat sink

6

retaining elements

7

retaining elements

8th

wave

9

Shape memory elements

10

pole

11

Through opening

12

feather

13

energy storage

14

abutment

15

blocking agent

16

Ringbahn

17

roll

18

position

19

attack surface

20

part

21

crankshaft

22

axis

23

crank

24

wheel

25

Rod

26

hole

27

The End

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19810639 A1 [0005]
• DE 19810640 C2 [0005]
• EP 0919717 A1 [0005]

Claims (14)

Heat engine, with one around a rotation axis ( 3 ) rotatable rotor ( 2 ) comprising at least one shape memory element ( 9 ), by rotating the rotor ( 2 ) between at least one heat source ( 4 ) and at least one heat sink ( 5 ) is adjustable, characterized in that the shape memory element ( 9 ) at least one on the rotor ( 2 ) arranged energy store ( 13 ) associated with the heat source ( 4 ) by a change in shape of the shape memory element ( 9 ) and at a defined circumferential position ( 18 ) outside the heat source ( 4 ) is dischargeable. Heat engine according to claim 1, characterized in that the energy store ( 13 ) Blocking agent ( 15 ), which is a discharge of the energy store ( 13 ) before reaching the defined circumferential position ( 18 ) are designed to prevent. Heat engine according to one of claims 1 or 2, characterized in that the energy store ( 13 ) a spring element ( 12 ) or from a spring element ( 12 ) consists. Heat engine according to claim 3, characterized in that the spring element in the heat source ( 4 ) by the change in shape, in particular by the contraction, of the shape memory element ( 9 ), at least approximately, linear, preferably parallel to the axis of rotation ( 3 ) of the rotor ( 2 ), is compressible or elongated and thereby rechargeable. Heat engine according to one of claims 3 or 4, characterized in that the spring element ( 12 ) at the defined circumferential position ( 18 ), at least approximately, linear, preferably parallel to the axis of rotation ( 3 ) of the rotor ( 2 ) is relaxing and thus dischargeable. Heat engine according to one of the preceding claims, characterized in that the shape memory element ( 9 ) is formed as an elongated element, in particular as a wire, or comprises an elongated element, in particular a wire, which, at least in the tensioned state, parallel to the axis of rotation ( 3 ) of the rotor ( 2 ) is arranged. Heat engine according to one of the preceding claims, characterized in that the shape memory element ( 9 ) between two parallel, transverse to the axis of rotation ( 3 ) of the rotor ( 2 ) extending, preferably disc and / or annular, retaining elements ( 6 . 7 ) is arranged. Heat engine according to one of the preceding claims, characterized in that means for converting the shape memory element ( 9 ) at the defined circumferential position ( 18 ) Energy are provided in a rotational movement and / or in electrical energy. Heat engine according to one of the preceding claims, characterized in that the rotor ( 2 ) with a part of the shape memory element ( 9 ) energy is drivable and / or that of the of the shape memory element ( 9 ) output energy independent drive for rotationally driving the rotor ( 2 ) is provided. Heat engine according to one of the preceding claims, characterized in that the shape memory element ( 9 ) is formed of a metallic shape memory alloy and / or a shape memory polymer. Heat engine according to one of the preceding claims, characterized in that a plurality of, preferably uniform, circumferentially spaced, preferably arranged on an imaginary circular ring, shape memory elements ( 9 ) are provided, each of which at least one energy storage ( 13 ), wherein at least two of the energy stores ( 13 ) spaced in time at the same circumferential position and / or at least two of the shape memory elements ( 9 ) at the same time at different defined circumferential positions are dischargeable. Heat engine according to one of the preceding claims, characterized in that at least two radially spaced shape memory elements ( 9 ) are provided. Heat engine according to one of the preceding claims, characterized in that the maximum temperature in the heat source ( 4 ) is lower than 100 ° C during operation, preferably higher than 80 ° C and / or that the temperature of the heat sink ( 5 ) is less than 60 ° C. System comprising at least one heat engine ( 1 ) according to one of the preceding claims and one by means of the heat engine ( 1 ) driven device, in particular a generator, and / or a pump and / or a vehicle.

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